It has, for some time, been recognized that the flow of certain fluids, such as crude oil, through a metal pipeline causes electrical currents to be built up in the pipeline. This electrical charge causes several problems. First, the existence of electrical charge and its subsequent discharge causes accelerated corrosion of the metal pipe such that the useful life of the pipeline is greatly diminished. In fact, in some geographical regions, it has been found that a metal pipe might deteriorate in less than one month's time when a petroleum product is transported through that pipe.
Another problem that is inherent at any time an electrical discharge current exists around a petroleum product is that of the combustion of the fluid or vapors therefrom. This danger of fires and the concomitant damage which the fires or explosions create is understandably of a very serious nature since, at a pump unit, abundant quantities of petroleum products are often present.
One problem, though, that has long plagued the oil field industry has been the degeneration of bearings and gears in the mechanical structure of the pump unit on a typical oil well. As should be appreciated, a typical pump unit has a support structure that forms a fulcrum for a cross beam that supports a counterbalance and a cable mount, and a motor or engine is operated to reciprocate the cable mount up and down. A draw cable is connected to the mount at one end and at the other end is connected to a carrier bar to the polish rod at the well head. This requires numerous gear trains and high tolerance bearing surfaces.
The pump unit reciprocates the cable mount which, in turn, correspondingly reciprocates the polish rod which, through its operation of the well sucker rod, withdraws the fluid from the well. Naturally, since there are great forces involved in pulling the fluid up out of the ground, especially in those areas where oil wells have been drilled several miles into the earth's crust, various bearing surfaces and gears must be of high strength and be very precisely ground.
While it is normally expected that the bearing surfaces and the gears of a well pump unit should have a lifetime of twenty to thirty years, in some regions this lifetime has been observed to be substantially shorter. Indeed, in certain regions along the border between the United States and Canada, it has been found that the bearings and gears of a well pump unit may deteriorate within one or two years. The standard corrective process has been to replace the bearings and gears at frequent intervals, but, until the present time, as explained in this application, no one has recognized the problem that causes this excessive wear and tear on the mechanical structure of the well pump unit.
Specifically, the present inventors have determined that the mechanical failure of gears and bearings within a well pump unit is due to electrical pitting. In the case of bearings, such electrical pitting destroys the smooth bearing surfaces necessary for high tolerance operation. When the surfaces become roughened, the bearings lock or jam, and the pump unit is disabled. This shut down is expensive both since there is lost revenue from the well and since the operative mechanisms of the pump system must be replaced. When gears become pitted, the teeth are weakened so that breakage of the gears may occur. When breakage occurs, small bits of metal become entrained in the gear lubricating fluid so that they continually eat at the turning gears as the device is operated. Over a period of time, similar shut down problems may result.
As noted, prior to the efforts of the present applicants, the problems due to the electrical currents that exist in a well which are present at the well head due to the conductive nature of the well casing had not been solved in a satisfactory manner. As a result of this discovery, by applicants, they recognized a need for a commercially viable method and apparatus that can prolong the useful life of the pump unit's gears and bearings by isolating these electrical currents from the well pump unit. Such a method and apparatus must make use of materials that can withstand the substantial forces that are present when pumping oil or other petroleum products from the ground and which are durable to stand the test of time.